This invention relates to a flow weigher for determining the weight and flow rate of a powder material in a continuous feed process, and more particularly to a loop-conveyor-type flow weigher for detecting the weight and flow rate of powder material by use of a loop conveyor which has a ring-shaped path for carrying or conveying such material.
Generally, powder has no fluidity except for a special kind of powder, which will be described hereinafter. Accordingly it is quite difficult to check the weight or flow rate of powder in any continuous powder feed system. This is not merely because of difficulty in the conveyance of powders at a constant rate, but also because of their quite different behavior depending on their type and environment.
There are used prior-art continuous powder flow weighers of a belt conveyor type where the weight of powder which is carried on the belt is checked in the process of transfer by means of the belt conveyor which is running straight, and those of a screw conveyor type where the weight of powder is determined in the process of screw conveyance.
In these weighing systems, however, some of powder or fine particles will stick to a belt or screw and other parts, even growing rather thick. Then, scale values obtained therefrom cannot be accurate due to increasing errors in the tare.
Known as a special kind of powder is powdered coal or pulverized coal, which has been used as fuel for large-scale burners. This material exhibits high fluidity and violent flushing. Conventional belt or screw conveyor type flow weighers as described above cannot be employed for this material. Such powder will flow out in a moment faster than the movement of a belt or run out instantly through a screw groove. This makes it impossible to detect the weight of this kind of powder.
An object of the invention is to provide a flow weigher which permits accurate detection of the weight and flow rate of powder in a continuous powder feed system.
Another object of the invention is to provide a flow weigher which permits constant-rate feed of such powder as pulverized coal, which may otherwise present a phenomenon of violent flushing, and accurate determination of the weight and flow rate of such powder.
Still another object of the invention is to provide a flow weigher which has several partition vanes between which section chambers are formed for carrying powder, especially powdered coal, said partition vanes having improved sealability.